There are numerous automatic retracting tape measure devices on the market to facilitate dispensing and retraction of tape. Often these devices incorporate an internal coil spring with one end attached to a spindle and the other end attached to a tape spool. The retraction feature results from the torsional bias imparted to the spool by the coil spring. Since the spindle is permanently fixed to the tape case the force imparted to the internal coil spring is generally constant and cannot be readily altered after assembly.
Certain assembly problems arise from the need to impart the requisite bias to the coil spring. The bias force must necessarily be imparted to the coil spring before the tape case is fully assembled. Assembly procedures often require partial assembly, with the tape spool end of the coil spring held in place, and the partial assembly rotated until the proper force is imparted upon the internal coil spring before the tape case itself can be fully assembled. This method of manufacture, which is necessitated by the structure of the device itself, frustrates automated assembly. These devices can lose their retracting ability when the internal coil spring begins to lose its resiliency. To compensate for this loss of resiliency a re-assembly or a re-manufacturing of the device is required.
The present invention overcomes the disadvantages discussed above by providing for a construction which permits adjustment of spring torsion after assembly. The construction of the invention facilitates automated assembly, without any change in the outward appearance of the device to the consumer.
As described in the preferred embodiment, the invention includes a ratchet wind retracting device with an externally accessible spindle. A ratchet assembly locks against the case to permit rotational movement of the spindle in one direction only. This allows the internal coil spring to be wound toward greater torsional bias after the case has been fully assembled. The features of such a ratchet assembly accomplish several objectives: (1) the new method of assembly allowed by the novel structure of this ratchet wind retracting device will facilitate the speed of automated production of the device; (2) the internal coil spring can be tightened from the exterior of the case as it loses its resiliency and its ability to effectively retract the tape; and (3) the force imparted upon the internal coil spring can be released and the spring unwound as the case is loosened, prior to disassembly.